Immunohistochemical detection of estrogen and progesterone receptors performed with an antigen-retrieval technique on methacarn-fixed paraffin-embedded breast cancer tissues.

Immunohistochemical detection of estrogen and progesterone receptors (ER and PgR, respectively) was performed in 67 cases of Japanese female invasive breast carcinoma on methacarn-fixed paraffin-embedded sections using monoclonal antibodies against ER (1D5) and PgR (10A9) with an antigen-retrieval technique based on microwave exposure in citrate buffer solution. Staining localized in nuclei and specimens containing > or = 20% specifically stained tumor cell nuclei were considered ER- or PgR-positive; the positive rate was 37% (25/67) for ER and 45% (30/67) for PgR. The immunohistochemical (IHC) results were compared with cytosolic receptors obtained from tissue homogenates as measured by dextran-coated charcoal (DCC) assay, in which tumors were considered ER- and/or PgR-positive when receptor concentration was greater than 3 or 5 fmol/mg cytosolic protein, respectively, and agreement between the two methods was 71.6% for ER and 80.6% for PgR. The sensitivity and specificity were 53.5 and 91.7% for ER-IHC, and 77.4 and 83.3% for PgR-IHC, respectively. In relation to age of the patient and stage of the cancer, ER immunoreactivity correlated with patient's age (> or = 55 vs 55, P = 0.032), and proportionally increased with aging (P = 0.0084) using the Kruskal-Wallis statistics. PgR-immunoreactivity correlated with nodal involvement (P = 0.031) by the TNM system. However, no correlations were found between the results of the DCC assay and any of the clinical parameters examined. Thus, immunohistochemical assay may provide valuable information in predicting prognosis and response to endocrine therapy.